Structures and optical absorptions of PbSe clusters from ab initio calculations

Area of Science:

• Materials Science
• Quantum Chemistry
• Solid-State Physics

Background:

• Understanding the structural and electronic properties of lead selenide (PbSe) clusters is crucial for their application in nanotechnology.
• Previous studies on II-VI clusters have highlighted significant structural diversity.

Purpose of the Study:

• To investigate the low-lying structures and growth patterns of (PbSe)n clusters (n=1-10).
• To identify stable building blocks within PbSe clusters.
• To analyze the impact of spin-orbital coupling on the electronic and optical properties of PbSe clusters.

Main Methods:

• First-principles molecular dynamics for identifying low-lying cluster structures.
• Density Functional Theory (DFT) for geometrical and electronic structure calculations.
• Time-dependent DFT (TD-DFT) with spin-orbital (SO) coupling for simulating UV-vis spectra.

Main Results:

• Two distinct growth patterns were predicted for even-n and odd-n (PbSe) clusters.
• (PbSe) clusters exhibit a preference for simple cubic and bulk-like structures.
• The (PbSe)4 cluster was identified as a highly stable building block due to strong Pb 6p-Se 4p orbital overlap.
• Spin-orbital coupling significantly reduces binding energy but does not alter relative cluster stability.
• SO coupling strongly influences the simulated UV-vis spectra of PbSe clusters.

Conclusions:

• PbSe clusters display unique growth behaviors compared to other II-VI clusters.
• The (PbSe)4 unit is a key stable motif in PbSe cluster formation.
• Spin-orbital coupling is essential for accurately predicting the optical properties of PbSe clusters.